1. Field of the Invention
Methods and apparatus for defrosting and heating certain frozen convenience foods (for example, fried egg rolls, fried chicken, fried sandwiches, hot corn beef sandwiches and baked and leavened products) in a microwave oven are described. This invention concerns the reconstituting of certain frozen, precooked foods, in a microwave oven, without using metal members, as exemplified by my U.S. Pat. Nos. 3,985,990 and 3,985,991, or microwave auxiliary heating elements, as exemplified in my U.S. Pat. No. 3,777,099, but capitalizing on some of the principles of heat transfer and microwave cooking taught in said patents.
2. Description of Prior Art
Frozen food, reconstituted in a microwave oven, tends to spot heat. This is attributed to the different loss factors of frozen vs. unfrozen portions of the same food. Moreover, flat portions of food, as a sandwich, tend to edge heat--for unlike the middle portion of a sandwich which can only receive microwave energy from its top and bottom, the edge of said sandwich receives its energy from its top, bottom and side. To overcome spot, selective and edge heating, it is taught to operate at reduced power levels and/or provide a resting interval, but reduced power levels and resting intervals undesirably increase the cooking time and can result in undesirable dehydration of a food.
In microwave cooking, microwave energy concentrates at the ends of cylindrical foods (as egg rolls and hot dogs) and foods with protuberances (as the ends of fried chicken wings) which results in uneven, undesirable heating. Prior art teaches to cover ends, edges and protuberances with aluminum foil shielding to combat this problem. In my U.S. Pat. No. 3,985,990, there is taught to perforate said aluminum foil shielding to permit the free release of water and oil food by-products while shielding said ends, edges and protuberances. This invention differentiates over my perforated aluminum foil shielding in that it accomplishes, in one operation, all the required shielding of said ends, edges and protuberances by overlaying a food with a novel structure which includes perforated, plastic film and a padding of microwave-permeable, liquid-absorptive material. Said padding of microwave-permeable, liquid absorptive material, in permitting the free random irradiation of a food by microwave energy, results in water being ejected from initially heated spot and edge portions of said food. Which ejected water is forced through a porous plastic film into a liquid-absorptive material. Whereupon the wet liquid-absorptive material becomes microwave-absorptive which thereupon selectively reduces the amount of microwave energy reaching the areas of food which initially evolved said water. This and further advantages of my discovery will become more apparent in the description that will follow.
The words "egg rolls" in this writing is meant to describe a cylindrical type, crusted, deep fat fried food whose filling may be of many varieties. For example, some fried "egg roll"]type products may contain pizza type fillings and others may contain white and/or dark meat, boneless chicken. When fried, packaged in my novel package and frozen, said deep fat fried, boneless chicken rolls, pizza rolls, Chinese egg rolls and the like will result in a desirable snack food product line for vending operations. Notwithstanding this special deep fat fried, batter crusted, boneless chicken "egg roll" snack product, the words "fried chicken" and "fried foods" used herein encompass their common connotation.
This invention is a continuation-in-part of my U.S. Ser. No. 927,397, filed July 24, 1978 now abandoned which is a continuation-in-part of my U.S. Pat. No. 4,103,431 where is described drying methods and apparatus for drying articles. In said Ser. No. 927,397 and U.S. Pat. No. 4,103,431 are taught, during microwave heating, to extend the physical size of an article by temporarily confining it within a microwave-permeable container which impedes the free release of vapor from said article so that said article will dry in a positive vapor of its own making. In said Ser. No. 927,397 now abandoned and U.S. Pat. No. 4,103,431, there are discussed the advantages of temperature monitoring of vapor pressure overlaying an article, wrapping an article in perforated high-temperature plastic film and employing a liquid-absorptive enclosure. This invention draws on the discoveries I made in said U.S. Pat. No. 4,103,431. This invention does not concern the uniform drying of my U.S. Pat. No. 4,103,431 or the selective heating of my U.S. Pat. Nos. 3,985,990 and 3,985,991, but concerns novel structure designed to defrost and heat certain foods which novel structure is also useful during shipping, storing, serving and/or eating of said foods.
In commercial and vending feeding, the faster an item can be heated, the longer it can be held hot, the convenience and simplification added by the package (for example, no requirement for knife and fork) and the ease of clean up are all important considerations which this invention is designed to afford.